Patent GB-600579-A (GB)
Title: Power steering mechanism
IPC: B62D5/10
Filed: 1945-06-09
Abstract: 600,579. Fluid-pressure servomotor-control systems. CLEVELAND, F. J. (Bendix Aviation Corporation). June 9, 1945, No. 14664. [Class 135] [Also in Group XXVI] A power steering mechanism for a vehicle of the kind in which movement of a manual control member operates a follow-up valve controlling a double-acting pressure-operated servomotor connected to the steering wheels and in which the valve comprises two parts, one of which moves as one with the servopiston, and the second part is connected to the first by a lever which acts about one fulcrum as a third order lever in response to movement of the control member and as a first order lever about another fulcrum in response to operation of the servomotor, is characterised in that the control valve is located outside but adjacent the servomotor, and that part of the valve which moves as one with the servo-piston is located between the ends of a rectilinearly movable member connecting the piston to the drag link. In an embodiment, rotation of a shaft 10 in the steering column moves a pitman 22 through a worm and sector unit, and rotation of the pitman causes a longitudinal movement of a tube 56 to which it is connected through the intermediary of a strap 25, the latter having an enlarged aperture giving a lost-motion pivotal connection with an idler lever 34. At the other end, tube 56 pivotally carries a tubular member 60 which is also pivotally connected at 142 to ears projecting from a valve casing 77, the latter being carried by a tube 126 secured at its other end to the piston 101 (see Group XXVI) of the servomotor. Tube 60 also has a pivotal connection at 68 with a floating lever 70 of which the ends are pivoted, respectively, to the valve casing at 78 and to a piston valve 93. When tube 60 is moved by rotation of the shaft 10, lever 70 pivots about point 78 and valve 93 is moved from the neutral position shown in which the two ends of the servomotor are inter-connected to a position in which a vacuum derived from the induction pipe of the engine through pipe 103 is applied through one of the sets of ports in valve seating sleeve 88, through a recess 84 or 86 in a block 80 in the valve casing, and through one of two concentric tubes 98, 126, to one side or the other of a diaphragm 100 carried inside piston 101. The two chambers defined in piston 101 by the diaphragm each connect to one of the two chambers of the servo-cylinder through ducts 117, 119, so that the movement of valve 94 applies suction to one side of piston 101 and the other side is put into communication with atmosphere through one of the tubes 98, 126, the valve 93, the inside of sleeve 88, the inside of a bellows surrounding tube 126, a pipe 125 and an air filter. The subsequent movement of piston 101, due to the differential pressure applied to its two sides, will move valve casing 77 and the sleeve 88 to re-centre valve 93, this re-setting motion being aided by lever 70 which will now pivot about point 68. Valve casing 77 is connected to a tube 58 which, at its other end, moves a bar 152 which is fast on idler lever 34 but has a lost-motion connection with pitman 22.. The drag link 132 is connected by a ball joint with bar 152. As tube 98 is connected to diaphragm 100, the differential pressure applied to the latter will be communicated back to the manual control member to give " feel." Should the force exerted by the servomotor prove insufficient, the physical force exerted by the driver will be added to the power effort after the various lost motion connections have been taken up.